License for an arcade game

[John Cowan]

Pimm Hogeling scripsit:

> I've started developing a new arcade game. I've decided that I want to
> keep the project as open as possible so everyone can contribute (code,
> graphics, sounds, even ideas), so they can make the game better for
> all of us. To me, this also means that others shouldn't be able to use
> the code in other works that are not open (such as commercial closed
> source projects). I have read that since GPL code can only be used in
> other GPL projects it will always remain open, so that sounds good to
> me. Keep in mind that I am not and do not have a lawyer.

What you want is a strongly reciprocal license ("strong copyleft").
That means, as you say, that any modified versions must be licensed under
the same license as the original.  There are several such licenses,
but the GPL has the advantage that lots of content is available under
it already and it is well-understood by the community.

> However, I have two (probably simple) questions about licensing the
> contents of my (or should I say "our") game.
> First, to make this project as compatible and open as possible I was
> thinking about using a dual MPL 1.1/GPL 3 license using section 13 of
> the Mozilla Public License. Considering my "as compatible and open as
> possible" and (maybe more important) "always remain open" statements
> above, would you recommend a MPL 1.1/GPL 3 license, or would a single
> GPL 3 or maybe even an other license be better in this case? I can
> find enough info on the GPL, but the MPL is still a bit unclear to me.

The MPL is a weakly reciprocal license.  MPLed code *can* be incorporated
into proprietary works, but only if any changes made to the MPLed code
itself (on a file-by-file basis) are made freely available under the MPL.
Since you do not want your content used in proprietary works at all,
you should avoid the MPL.

> Second, the game is obviously not only code. It will also contain
> graphics, sounds and maybe other resources. How should they be
> licensed? Let's say I license the code as MPL 1.1/GPL 3, does this
> mean the game (package) can only contain material (other than code,
> that is) with a certain license?

No.  First of all, you as the licensor are not bound by your own license.
Second, works under the MPL can be incorporated into larger works under
any license, provided the rule explained above is followed.

> Could a Creative Commons license do the trick?

There is no reason not to simply place the non-code resources under
the GPL.

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